Such a heat exchanger is useful in particular as a condenser in an air conditioning installation for a motor vehicle. A heat exchanger of this kind is described in the specification of published European patent application No. EP 0 377 936A, in which the tubular wall of the manifold is formed with diametral slots, with each baffle being introduced laterally through one of these slots and having an appropriate contour such as to enable it to come into abutment against the ends of the slot. The baffle, thus located in position, is subsequently brazed to the tubular wall. A disadvantage of this arrangement is that the manufacture of the tubular wall is complicated by the need to machine the slots, while the shape of each baffle has to be irregular. In addition, the slots form sites for possible leakage.